Hmm, I've never tried jumping a Darkie up to the Piers...
As Rebs - Spawn at a Pier, run to the farther stairway (not the nearest one), blow away their first wave and try to take the Dock. It takes me a few tries, but I can usually get it. Once I have it, I toggle between defending it, defending the other Pier, and taking the Landing. I generally ignore the AT-STs, let the AI turrets and vanguards deal with them. It's a struggle at first, but as their numbers wear thin, it becomes easier to push out toward their CPs. Also, they'll often abandon Walkers, so watch for a chance to steal one.
As Imps - Spawn at the back, get in a walker, march up the middle, pause at an R5 to heal up while destroying any turrets, then march to a pier (I'm partial to the left Pier). Get out, go up the rope bridge, take the CP and keep turning around while you do. No matter what direction you face, the game will find a way to spawn someone directly behind you
Once you have it, just keep defending until they run out of guys. Make sure you support the Landing, as that's the first thing they go for.
As Seps - same thing, except with an AAT.
As Repubilc - I don't usually play Republic. Stealing an AAT sounds like a good plan though.